Telephone device



"Patented Aug. 14', 1928.

UNITED STATES PATENT OFFICE.

FRANK CONRAD, OF PITTSBURGH, PENNSYLVANIA, ASSIGNOR TO WESTINGHOUSE ELECTRIC & MANUFACTURING COMPANY A CORPORATION OF PENNSYLVANIA.

TELEPHONE DEVICE.

Application filed December 7, 1923. Serial No. 679,075.

This invention relates to telephone receivers and is particularly adapted to loudspeaking telephones. Such telephones are frequently built with four coils, mounted two on each pole. Usually, a movable armature is positioned between the adjacent ends of the'coils' and, while the instrument is working, some flux traverses the armature lengthwise.

It is one object of my invention to reduce the magnetic reluctance without materially increasing the inertia of the armature.

It is a further object of this invention to provide a train of movingparts, extending 1 from the support of the armature to the diaphragm, without using, at any point thereof, a joint which will permit'relative mot-ion of the joined elements. All relative motion of the several parts of vided for by elastic deformation of some art, no lost motion is possible. An object of this invention, incidental to providing'a connection free from all lost motion and uniting the movable armature and the diaphragm, is the provision of a fastening between the connecting link and the diaphragm, which fastening may be easily and inexpensively manufactured, will add butlittle to the weight of the diaphragm and will not work loose-as the device is used.

It is a further object provide an armature of maximum stiffness, minimum weight and having its maximum area of cross section where the flux to be transmitted is greatest. This also provides the increased cross-section witha minimum a corresponding increase in the moment of inertia of the. armature.

It is a further object of this invention to provide a method of manufacturing parts and assembling the device which will produce the correct clearness between the movable armatureand the adjacent ends of the of this invention to 4 cores of the coils without requiring 7 anexcessive amount ofskilled workmanship.

, In telephones heretofore used, of the type having a tiltin armature drivinga diaphragm, none of the above stated objects are accomplished, with the consequence that ob- -je ctionable overtones occur in such telephones and that they are less eflicient.

It is'a further ob ect of my invention to provide an assembly in which the permanent is locat ed under the cross bar 32. The plate at fl gnet does not act "as, a support.

the train being pro-' gether by a of suitable insulating material.

It is a further objectof my invention to provide securing means for holding the permanent magnet in place which require no operation upon the magnet tending to decrease its magnetization.

Other objects of this invention and details of the construction will be apparent from the following drawings, in which Figure 1 is a topplan view of the device, with the cover removed, 0

Fig. 2 1s a section upon the line 2--2 of Fig. 1, Fig. Fig. 1,

Fig. 4 is a detail view, in perspective and on a larger scale, of the armature,

lig. 5 is a plan view of the diaphragm, an

Fig. 6 is a plan view of an insulating plate.

The magnetic circuit 3 isa section upon the line 3-3 of utilized in this teledescription "and from the phone instrument includes a permanent magnet 10,-one end of which is held in contact with a cross piece 11, which constitutes a pole piece. These parts are fastened tobridge 12, fitted to the end. of the permanent magnet and attached to the pole piece 11, by the screws 13. The permanent magnet 10 extends through a right angle, and the pole opposite the bridge 12 contacts with a base plate 14. The cross piece 11 and the base plate 14 are parallel and between them extend posts 15, of brass or other non-magnetic material, which receive the screws 13 at their upper ends and, at their lower ends, are fastened to the base plate 14 by screws 16. Midway, these posts are notched, as indicated at 17 in Fig. 3, to receive the ends of a strip of phosphorbronze 18, which is secured to the posts by a screw at each notch.

Four cores, 20, 21, 22 and 23 are secured to the cross piece 11 and to the base plate 14, respectively, by screws 24,25, 26 and 27. Upon each core is wound a coil. The coils are connected as will be explained below, and their ends are connec conductors 28 and 29, to binding posts 30 and 31, which. are mounted in a cros bar 32 the binding sts 30 late 14, a plate 33 of insulating material ted, by flexible 33 is provided with a rectangular opening 34 which serves to receive the lower end of the magnet 10 and hold it in place. The plate 33, bar 32 and binding posts 30 and 31 are all secured to the base plate 14 by a bolt 35, and a hole 36 is provided in the plate 33 for this purpose. Corresponding holes are, of course, provided in the bar 32 and the base plate 14. 1

This plate is also provided with a large central opening 37 through which the link 38 extends to the center of the diaphragm 39. The diaphragm 39 is located in a chamber, one wall of which is constituted by the base plate 14. The other wall is formed by a cap 41. The opening 37 is of suflicient area to ail-0rd free movement of the air between the diaphragm 39 and the base plate 14. The damping of the diaphragm on this side is thus reduced to a minimiun. The opening 37 is, however, small enough to leave, in the base late 14, an abundant cross-sectional area or conducting the flux from the lower end of the magnet 10 to the cores 22 and 23.

The cap 41 is provided with a central opening 42 surrounded by a boss 43, wh ch is threaded upon the inner face to receive either the end of a horn or an adapter, whereby various styles of horns may be accommodated. Although the opening 42, as illustrated, has an area equal to or exceeding that of the opening 37; when the horn is in place, the effective opening in the cap is smaller than that in the base plate, and preferably much smaller.

Between the opening 42 and the edge of the cap, a shoulder 44 is provided, which cooperates with the base plate 14 to form a groove for receiving the edge of the diaphragm. The shoulder is covered with a layer of cushioning material 45. Preferably varnished cloth, of the kind known as empire cloth, is employed, but any elastic material of sufiiciently uniform character will serve. It should be a thin material in order that the space between the diaphragm and the cap shall not be increased unduly. The cementitious action of the varnished cloth helps to hold the diaphragm in position.

On the other sid of the diaphragm, the groove is filled with a thicker cushioning material. A soft rubber washer 46 is employed for this cushion. The combined thickness of the. and the diaphragm exceeds he,ca to the base As shown on the drawing, there are six of these screws and two of them are accommodated by notches in the plate 33 of insulating material. The radius of the diaphragm is slightly less than that of the bottom or vertical wall of the groove, the diaphragm being held in place by the clamping and the cementitious action, without any binding of its edges against the bottom of the groove. This method of fastening lessens the tendency-for the diaphragm to set up its own period of vibration.

The rod 38 is secured to the center of the diaphragm 39. It is important that the junction between the two he very rigid and add as little as possible to the weight of the diaphragm at this point. Moreover, no operation involving high heat, such as soldering or brazing, may be employed in making this joint, because the temper and, consequently, the elasticity of the diaphragm would be altered thereby.

In order to provide a these requirements, the lower end of the rod 38 is threaded, and a pair of nuts, one on each side of the diaphragm, are secured thereon. To afford good bearing surfaces, each of the nuts is separated from the diaphragm itself by a washer. The threads are very fine, the nuts small and the washers thin, tosecure as light a joint as possible. When the washers are in place, the nuts may be turned up tightly without injury to the diaphragm. After the nuts are tightened, a cementitious material is applied to them, which, upon hardening, leaves them securely fastened on the threads. All danger of the joint working loose is thereby avoided.

1e armature consists of a thin flat sheet of soft iron, mild steel or other highly permeable material. It is stiffened by ha vingits edges turned through a right angle, forming anges, as shown at 54. At the two ends, the width of the armature slightly exceeds the dlmneter of cores of the coils. the armature is of circular outline, as shown at 55, so that it projects uniformly beyond the edges of the cores. At the other end, however. the edges of the armature are continued along straight lines to afford two extensions 56, one on each side of the notch made by bending the tab 53 described below. The fianges are thus extended well beyond the brazed oint to ensure stiffness of the armature at the point where the load is applied to it.

he armature is made wider at the middle than at either end, and the edges extend in a pair of straight converging lines from the wide central portion to joint that shall meet WISC- eores. At the central parts, therefore, the armature must carry the whole of the flux,

. there. because while, at the end portions, it carries'onl a part thereof, some of .the flux having eft the armature and gone into portions of the cores nearer thecenter of the armature. The greater width at the middle of the armature provides a greater cross-sectional area the armature is of uniform thickness. Thus, the cross section is greatest where the filix to be carried-is greatest, avoiding any excessive flux density.

The cnd of the rod 38 is secured to the armature 51 by a brazing operation. In order to facilitate this, the end of the rod 38 is flattened, as shown at 52, and a tab is made by bending a'portion of the armature through a right angle, as shown at 53. Since these parts are very small, the necessity for obtaining an ample surface to make the brazed joint will be evident.

At the middle of the two turned-up edges, the material is'prolonged to form a pair of stirrups' .58, each containing a notch to receive thestrip 18 of phosphor bronze.

The cap 41 is supplied'with two diametrically opposedfpins 61, which are intended to co-operate with grooves 62, forming a bayonet fastening by which the cover 63 is held over the apparatus. The cover is provided with ahole having a soft-rubber bushing 64 through which the cable for the 1 electrical connections 1s introduced. The

length.

' but must be securel phosphor bronze. is of the stirrups 58,

brazed to the diaphragm ots, hinges, or other joints.

ends of the cable extend to the binding osts 30 and 31 and are connected to the eads 28 and 29 already described.

The magnet 10 is of tungsten steel and very hard. It cannot be welded to the soft iron pole piece 11 orto the base plate 14 accomplished by t e bridge piece 12 and the insulating plate 33, each .of which i closely fitted to the end of the magnet.

In assembling the device, the strip of inserted in the notches and the armature and The rod 38 is tab 53, the rod secured to the by its nuts, the cement applied thereto and heated slightly to make it set. Thus, the whole moving system is .united into one body containing no bearings, pivstrip are soldered together.

The plate 14" s ground upon both faces.

.Grinding the face toward .the cap ensures av good fit between thebase plate and the the other face of the base the brass posts 15. The posts have both ends ground so that: they are of a definite This surface of the cross piece 11' facing these posts is also ground. ,The accuracy. of the distance between the opposite surfaces of the pole piece 11 and. the base plate 14 is thus ensured.

It will be noted that this method of assembling providesthe accurate spacing the thin sheet material of the armature perdescription to Fig.

heldin place. This is nates, the armature 1s elasticity movement... The resistance of the diaphragm without requiring any machining, grinding, or other operation upon the permanent magnet.

The cores of the several coils also are ground to an exact length, so that, when the coils are attached to the base plate 1 1 and the cross piece 11, respectively, the dis tance between the adjacent ends of the cores will be accurately fixed. Since this distance is very small and the reluctance of the magnetic circuit depends very greatly upon it, the importance of accurate fitting will be evident. In grinding the cores, care I should be taken to have their end surfaces perpendicular to their axes. This ensures that the axes of the cores will be at right angles to the planes of the cross piece and the base plate and, therefore,that the alinement of the cores will be correct.

As the remainder of the operation of acsembling the devicewill be obvious to any skilled mechanic, no detailed description thereof is deemed necessary.

The two cores attached to the north end of the magnetic, circuit present north poles to the armature and the two opposite cores present south poles to the other face of the armature. When the flux is undisturbed by any current in the coils, it passes through pendicularly, producing no flux lengthwiseof the armature. I

The directionof the winding in each of the several cores is such that, applying the 2, with one direction of current, the pole strength of the left-hand north pole and of the right-hand southpole is increased, while the pole strength of the left-hand south pole and the right-hand north pole is diminished. This results in a flux from left to right in the armature 51.

With the current in the opposite direction, the right-hand north pole and the lefthand south pole are strengthened, while i the right-hand south pole and the left-hand 1l0 north pole are diminished. This will result in a flux from right to leftin the armature. Consequently, as the current alter-.

tilted. first in one direction and then. in the other, the tilting 11 being accompanied by a slight torsion in "the strip 18. At the same time, the diaphragm ,39- is flexed, first in one direction and then inthe other will be evident that,-so faras the magnetic forces are concerned, when the arma true 51 is in mid position and nocurrent is flowing-it is in equilibrium, but the equi-. llbllllm s-unstable,-and a -very slight disturbance of the magnetic forces is, therefore, accompanied by a tendency of thearmature to move to an extreme position. Only the torsion in the strip 18. and the of :thediaphragm 39 oppose this said to the flexing action of the rod'38 is made as small as possible by introducing corrugations. The strip of phosphor bronze 18 is highly elastic and the torsion introduced by the motion of the armature is slight, because this motion is small. Consequently, the resistance to the armature movement is slight. A very small mount of energy is, therefore, enough to maintain the vibration of the iaphragm. It will, therefore, be vident that the telephone is extremely sensitive.

am aware that numerous details in the construction may be varied through a wide range without departing from the spirit of this invention. I, therefore, do not purpose to be limited except as necessitated by the prior art or indicated by the claims.

claim as my invention:

1. In a loud-speaker telephone, a magnetic circuit having an air gap and a bifurcation at each side of the air gap, the portions of the magnetic circuit constituting the bifurcated parts being united to the remainder of the circuit by ground joints each joint being transverse to the length of the air gap.

2. In a loud-speaking telephone, a base plate, a diaphragm on one side of said base plate, mechanism for moving said diaphragm upon the other side of said base plate, said mechanism including a magnetic circuit of which the base plate forms a part.

3. In a loud-speaking telephone, a base plate, a diaphragm on one side of said base plate, mechanism for moving said diaphragm upon the other side of said base plate, said mechanism including a magnetic circuit of which the base plate forms a part, said base plate having an orifice, a connection between said mechanism and said diaphragm extendin through said orifice, the material around aid orifice having greater cross-section than some other parts of the. magnetic circuit.

4. In a loud-speaking telephone of the type having an air gap with four pole pieces around it, an armature mounted in said air gap, a support for said armature, said sup port extending between said pole pieces, a rigid connection between said support and armature and a rigid connection between said support and said pole pieces,

5. In a device of the class described, an armature comprising a flat body having two stirrups at opposite ed es and a torsional mounting secured to sai stirrups.

In a device of the class described, an

- armature comprising a substantially flat body of magnetic sheet material having upturned edges and tapering from its middle section towards each end.

7. In a device of the class described, two pairs of pole pieces, an armature mounted between them, with one end between the members of each pair and having a substantially flat body of magnetic sheet material,

each end of said armature being approximately equal to the cross-section of the field of the corresponding pair of pole pieces, the ed es of said armature divergin toward its mi d-portion whereby the widti of the armature is greater at its mid-portion.

8. In a device of the class described, an armature of magnetic sheet material having a substantially fiat body and up-turned edges.

9. In a device of the class described, an armature of ma netic sheet material having a substantially fiat body and up=turned longitudinal edges, said up-turned edges terminating short of one extremity of the armature.

lO. In a device of the class described, an armature of magnetic sheet material having a substantially flat body and up-turncd longitudinal edges, said up-turned edges extending beyond the loading point, and a reciprocating connection attached to the armature at the loadin point.

11. In a magnetic evice having an armature,a rod for attaching the load to the armature and means in -the armature for stiffening it adjacent the point of attachment.

12. In a device of the class described, a substantially flat armature having up-turned edges, forming flan es, stirrups at the middle part of each a e, and a mounting strip secured to said-stlrrups.

13. In a device of the class described, a substantially fiat armature having up-turned edges constituting flanges, a tongue adjacent one end of said armature, constituting means for attaching the load, said flanges extending beyond said attaching means at this end of the armature.

14. In a device of the class described, a substantially flat armature having upturned edges constituting flanges, a tongue adjacent one end of said armature constituting means for attachin the load, said flanges extending beyond said attaching means at this end of the armature and terminating short of the other end of said armature.

15. In a; device of the class described, a base plate having a ground surface, a magin: netic circuit including said base plate and a pole, piece toward said base plate also having a ground surface, non-magnetic posts having ground ends and rigidly conmeeting said pole piece to said base plate,,120 whereby the distance between said base plate and said pole piece is accurately fixed, and magnetic members of accuratel -determined length rigidly secured respectively to said base plate and said pole piece, the length of 125 said members being less than said distance, whereby an air gap of accurately predetermined width is produce 16. Ina device of the class described, a permanent magnet, a base plate constituting. o

part of the magnetic circuit, coils co perating with said magnetic circuit, binding posts connected to said coils, an insulating support for said binding posts and a member of insulating material separating said support from said base plate, said member also securing said permanent magnet in place on said base plate.

17. Ina device of the class described, a permanent magnet, a base plate constituting part of the ma netic circuit, coils co-o aerating with sai magnetic circuit, bin ing posts connected to said coils, an insulating support for said binding posts, a sheet of insulating material surrounding the end of said permanent magnet adjacent said base plate and separating said support from said. base plate, and afastening means' securing said support,

separating sheet and base plate together.

18. In a device of the class described, a corrugated diaphragm having a flat central area, washers on each side of the diaphragm engaging said flat area, a threaded rod traversing said washers and diaphragm, and nuts on said rod engaging said washers for attaching said diaphragm and said rod together, each of said nuts being locked in position by a cementitious material.

19. In a loud speaking telephone instru ment, an electro-magnetically oscillated armature, a diaphragm a connection integnlly uniting said armature and said diaphragm.

20. In a loud-speaking telephone, an armature, a support therefor, permitting the armature to oscillate, a flexible diaphragm, a connection uniting said. diaphragm an armature, the whole system, from said support to said diaphragm, inclusive, constituting one integrally united body.

21. In a loud-speaking telephone instrument, an oscillating armature, a vibratory diaphragm, a connection between said diaphragm and said armature, a support for said armature and a frame to which said support and said diaphragm are secured, joints uniting said parts into an integral whole,

each of said joints having means preventing relative motion between joined surfaces.

22. In a telephone loud-speaking instru-- ment, a magnetic circuit composed of stationary parts, a diaphragm, a means for vibrating the same, said diaphragm and said means constituting a moving system, and supporting connections between said moving system and said magnetic circuit, all of the joints in said moving system and said connections having means for preventing relative motion of the joined surfaces.

- diaphragm vibrated thereby andtially flat body of -magnet having a right-angle 23. In a sound producing ap aratus, a diaphragm, driving means there or, and a support for said driving means, said support, driving means and diaphragm being unite by joints and each of said joints having motion-preventing material applied thereto.

'24. In a sound-producing device, a diaphragm and a housing a horn-supporting cap on one side of saidand a base plate on the other side thereof, said cap having an orifice for communication with the horn and said base plate having an orifice of sufficient size to prevent damping of the diaphragm by' the air between it and said base plate.

25/In a sound-producing device, a diaphragm and a driving means therefor, a housing enclosing a diaphragm and having an opening'through which a portion of sai driving means extends, said opening being of sufiicient size to prevent damping of the diaphragm by air enclosed between it and the housing on the side of the diaphragm toward said driving means.

26. In a loud-speaking telephone, a base plate, a diaphragm on one side of saidbase plate, mechanism for moving said diaphragm mainly upon the other side of said base plate, said mechanism including a magnetic circuit of which the base plate forms a art.

27. In an electromagnetic instrument, a magnetic circuit having two air gaps in one plane, an armature comprising a substanmagnetic material in said plane, said body tapering from its middle section toward each end, said middle section being between said air gaps.

28. In an electromagnetic instrument, a magnetic circuit comprising a permanent magnet having two poles at right angles to each other and other members at right angles to each other co-operating nent magnet to form a magnetic circult of generally rectangular form, said other members being so secured with reference to said permanent magnet that relative motion therebetween is prevented.

29. In a telephone device, a permanent bar bend whereby it constitutes two sides of a rectangular -magnetic circuit,,a pair of pole pieces constituting a third side of said circuit and having an air gap between them, and a base plate constituting the fourth side of said circuit.

In testimony whereof, I have hereunto subscribed my name this 27th day of November, 1923.

FRANK CONRAD.

therefor, including with said perma- 

